diff --git a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
--- a/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
@@ -8,7 +8,9 @@
 
 #include "RISCVTargetTransformInfo.h"
 #include "MCTargetDesc/RISCVMatInt.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/Analysis/VectorUtils.h"
 #include "llvm/CodeGen/BasicTTIImpl.h"
 #include "llvm/CodeGen/CostTable.h"
 #include "llvm/CodeGen/TargetLowering.h"
@@ -323,6 +325,31 @@
     return LT.first * getLMULCost(LT.second);
   }
 
+  if (isa<FixedVectorType>(Tp) && Kind == TTI::SK_PermuteSingleSrc &&
+      Mask.size() >= 2) {
+    std::pair<InstructionCost, MVT> LT = getTypeLegalizationCost(Tp);
+    MVT EltTp = LT.second.getVectorElementType();
+    // If the size of the element is < ELEN then shuffles of interleaves and
+    // deinterleaves of 2 vectors can be lowered into the following sequences
+    if (EltTp.getScalarSizeInBits() < ST->getELEN()) {
+      auto InterleaveMask = createInterleaveMask(Mask.size() / 2, 2);
+      auto DeinterleaveMask = createStrideMask(Mask[0], 2, Mask.size());
+      // Example sequence:
+      //   vsetivli	zero, 4, e8, mf4, ta, ma (ignored)
+      //   vwaddu.vv	v10, v8, v9
+      //   li		a0, -1
+      //   vwmaccu.vx	v10, a0, v9
+      //   vmv1r.v	v8, v10
+      if (equal(InterleaveMask, Mask))
+        return 4 * LT.first * getLMULCost(LT.second);
+
+      // Example sequence:
+      //   vnsrl.wi	v10, v8, 0
+      if (equal(DeinterleaveMask, Mask))
+        return LT.first * getLMULCost(LT.second);
+    }
+  }
+
   return BaseT::getShuffleCost(Kind, Tp, Mask, CostKind, Index, SubTp);
 }
 
diff --git a/llvm/test/Analysis/CostModel/RISCV/shuffle-interleave.ll b/llvm/test/Analysis/CostModel/RISCV/shuffle-interleave.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Analysis/CostModel/RISCV/shuffle-interleave.ll
@@ -0,0 +1,57 @@
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 2
+; RUN: opt < %s -passes="print<cost-model>" 2>&1 -disable-output -mtriple=riscv32 -mattr=+v | FileCheck %s -check-prefixes=CHECK,RV32
+; RUN: opt < %s -passes="print<cost-model>" 2>&1 -disable-output -mtriple=riscv64 -mattr=+v | FileCheck %s -check-prefixes=CHECK,RV64
+define <8 x i8> @interleave2_v8i8(<4 x i8> %v0, <4 x i8> %v1) {
+; CHECK-LABEL: 'interleave2_v8i8'
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 15 for instruction: %concat = shufflevector <4 x i8> %v0, <4 x i8> %v1, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %res = shufflevector <8 x i8> %concat, <8 x i8> poison, <8 x i32> <i32 0, i32 4, i32 1, i32 5, i32 2, i32 6, i32 3, i32 7>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret <8 x i8> %res
+;
+  %concat = shufflevector <4 x i8> %v0, <4 x i8> %v1, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %res = shufflevector <8 x i8> %concat, <8 x i8> poison, <8 x i32> <i32 0, i32 4, i32 1, i32 5, i32 2, i32 6, i32 3, i32 7>
+  ret <8 x i8> %res
+}
+
+define <8 x i32> @interleave2_v8i32(<4 x i32> %v0, <4 x i32> %v1) {
+; CHECK-LABEL: 'interleave2_v8i32'
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 15 for instruction: %concat = shufflevector <4 x i32> %v0, <4 x i32> %v1, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 8 for instruction: %res = shufflevector <8 x i32> %concat, <8 x i32> poison, <8 x i32> <i32 0, i32 4, i32 1, i32 5, i32 2, i32 6, i32 3, i32 7>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret <8 x i32> %res
+;
+  %concat = shufflevector <4 x i32> %v0, <4 x i32> %v1, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %res = shufflevector <8 x i32> %concat, <8 x i32> poison, <8 x i32> <i32 0, i32 4, i32 1, i32 5, i32 2, i32 6, i32 3, i32 7>
+  ret <8 x i32> %res
+}
+
+; Should be expensive on RV32 because it can't widen
+define <8 x i64> @interleave2_v8i64(<4 x i64> %v0, <4 x i64> %v1) {
+; RV32-LABEL: 'interleave2_v8i64'
+; RV32-NEXT:  Cost Model: Found an estimated cost of 35 for instruction: %concat = shufflevector <4 x i64> %v0, <4 x i64> %v1, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; RV32-NEXT:  Cost Model: Found an estimated cost of 70 for instruction: %res = shufflevector <8 x i64> %concat, <8 x i64> poison, <8 x i32> <i32 0, i32 4, i32 1, i32 5, i32 2, i32 6, i32 3, i32 7>
+; RV32-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret <8 x i64> %res
+;
+; RV64-LABEL: 'interleave2_v8i64'
+; RV64-NEXT:  Cost Model: Found an estimated cost of 15 for instruction: %concat = shufflevector <4 x i64> %v0, <4 x i64> %v1, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; RV64-NEXT:  Cost Model: Found an estimated cost of 30 for instruction: %res = shufflevector <8 x i64> %concat, <8 x i64> poison, <8 x i32> <i32 0, i32 4, i32 1, i32 5, i32 2, i32 6, i32 3, i32 7>
+; RV64-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret <8 x i64> %res
+;
+  %concat = shufflevector <4 x i64> %v0, <4 x i64> %v1, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %res = shufflevector <8 x i64> %concat, <8 x i64> poison, <8 x i32> <i32 0, i32 4, i32 1, i32 5, i32 2, i32 6, i32 3, i32 7>
+  ret <8 x i64> %res
+}
+
+; TODO: getInstructionCost doesn't call getShuffleCost here because the shuffle changes length
+define {<4 x i8>, <4 x i8>} @deinterleave_2(<8 x i8> %v) {
+; CHECK-LABEL: 'deinterleave_2'
+; CHECK-NEXT:  Cost Model: Found an estimated cost of -1 for instruction: %v0 = shufflevector <8 x i8> %v, <8 x i8> poison, <4 x i32> <i32 0, i32 2, i32 4, i32 6>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of -1 for instruction: %v1 = shufflevector <8 x i8> %v, <8 x i8> poison, <4 x i32> <i32 1, i32 3, i32 5, i32 7>
+; CHECK-NEXT:  Cost Model: Found an estimated cost of -1 for instruction: %res0 = insertvalue { <4 x i8>, <4 x i8> } poison, <4 x i8> %v0, 0
+; CHECK-NEXT:  Cost Model: Found an estimated cost of -1 for instruction: %res1 = insertvalue { <4 x i8>, <4 x i8> } %res0, <4 x i8> %v1, 1
+; CHECK-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret { <4 x i8>, <4 x i8> } %res1
+;
+  %v0 = shufflevector <8 x i8> %v, <8 x i8> poison, <4 x i32> <i32 0, i32 2, i32 4, i32 6>
+  %v1 = shufflevector <8 x i8> %v, <8 x i8> poison, <4 x i32> <i32 1, i32 3, i32 5, i32 7>
+  %res0 = insertvalue {<4 x i8>, <4 x i8>} poison, <4 x i8> %v0, 0
+  %res1 = insertvalue {<4 x i8>, <4 x i8>} %res0, <4 x i8> %v1, 1
+  ret {<4 x i8>, <4 x i8>} %res1
+}